Secondary stroke prevention with antiplatelet drugs: have we reached the ceiling?

Patients with transient ischemic attack (TIA) or ischemic stroke carry a risk of recurrent stroke of between 5% and 20% per year. In patients with TIA or ischemic stroke of non-cardiac origin, antiplatelet drugs are able to decrease the relative risk of stroke by 11-15% and the risk of stroke, myocardial infarction, and vascular death by 15-22%. Aspirin is the most widely used drug. It is affordable and effective. Low doses of 50-325 mg aspirin are as effective as high doses and cause less gastrointestinal side-effects. The combination of aspirin with slow-release dipyridamole is superior to aspirin alone for stroke prevention but not for the prevention of cardiac events. The risk of major bleeding complications is not increased with the combination, which suggests that dipyridamole might act in another way than as antiplatelet drug. Clopidogrel is not superior to aspirin in unselected stroke patients but is superior in patients at high risk of recurrence. The combination of aspirin plus clopidogrel is not more effective than clopidogrel alone, but carries a higher bleeding risk. The most effective antiplatelet drugs, the GP IIb/IIIa antagonists, are not superior to aspirin and carry a higher risk of bleeding. These results indicate that any antiplatelet therapy with a more potent drug than aspirin will only have a marginally higher efficacy, which might be offset by a higher bleeding rate. Therefore, selection of patients who might benefit from antiplatelet therapy other than aspirin is important.